Television transmitting apparatus



Hume R. HARDING, JR ,43,%

TELEVISION TRANSMITTING APPARATUS Filed Dec. 19, 1935 INVENTOR foam- 7/%4PD//V6 JR f ea; flaw ATTORNEYS Patented June 9, 1936 UNITED STATESPATENT OFFICE 2,043,245 TELEVISION TRAN SMITTING APPARATUS RobertHarding, Jr., Elmsford, N. Y., assignor to National TelevisionCorporation, Wilmington, Del., a corporation of Delaware ApplicationDecember 19, 1933, Serial No. 703,063

14 Claims. (Cl. 178-6) This invention relates to television transmittingapparatus and especially to a system in which the picture is scanned insuccessive lines.

One of the objects of the invention is to provide a transmitting systemin which the illumination of the background of the reproduced picturemay be controlled.

Another object of the invention is to provide a separate light-sensitivecell or cells with a suitable amplifier therefor'directly in front ofthe scanning apparatus to operate from the projected light of theso-called flying spot instead of by reflection.

. Other objects of the invention will be apparent as the description ofthe invention proceeds.

The invention is illustrated in the accompanying drawing in which:

Fig. 1 is a diagrammatical representation of a transmitting systemarranged in accordance with the invention; and

Fig. 2 is a diagrammatical representation of a modified form of thecontrolling means for the light-sensitive cell used to pick up thebackground light.

Referring more specifically'to Fig. 1, a conventional flying spotscanning apparatus is shown in which light from an arc lamp lil, mountedin a suitable housing H, is directed against a scanning disc l2 which isrun at a constant speed by a suitable synchronous motor l3. An opticalsystem 14 projects light coming through the scanning disc on to theobject 15 to bescanned. A plurality of light-sensitive cells I6, mountedpreferably in light converging reflectors 11, pick up the reflection ofthe light falling upon the object l5 in a manner well known in the art,the cells being connected by wires l8 to an amplifier l9 and thence bymeans of wires 20 directly to the receiving apparatus (not shown) or tosuitable broadcasting apparatus for broadcasting the picture signal.

The operation of the scanning disc, which may be similar to the wellknown Nipkow disc causes a single spot of light at a time to cross theobject field in a horizontal line, striking the object tobe televisedand actuating the light-sensitive cells by reflection from the surfacethereof. When one spot has moved across the object another spot followsthus completely scanning the object.

It has been the usual practice to stand the ob ject to be televised upagainst a screen so that the spot sweeping across the object fieldcrosses not only the object to be televised but the background screen aswell, and the reflection from this background screen produces thebackground for the reconstructed picture. In the present invention Iprovide a background screen 2| of ground glass or other translucentmaterial and behind this screen I position one or more lightsensitivecells 22 mounted, if desired, in suitable reflectors 23 and connected bywires 24 to an independent amplifier 25 whose output may be connected tothe amplifier I9 by means of the wires 26. A suitable control knob 2'!permits the output of the light-sensitive cells 22 to be adjusted asdesired.

During the operation of my improved system the object to be scanned ispositioned in a dark room in front of the background screen 2|. The onlylight reaching the object is the flying spot of light from the scanningapparatus. It will be evident that when the spot of light is on theobject there is no light falling on the background screen 2|, but whenthe light passes off one side of the object so that the object is nolonger in the path of the projected ray it will'fall directly upon thescreen, providing, of course, that the object is smaller than the objectfield covered by the flying spot. When the apparatus is operating,therefore, the actual appearance of the background scre'en 2| is asindicated in the figure, the shadow 28'of the object appearing on thescreen.

Whenever the light spot is on the object the light-sensitive cells I6will respond, getting their light by reflection, and whenever the lightis on the screen 2| outside of the shadow 28 the cells 22 will respondwhile the cells [6 give no response or very little. As the output of thecells 22 may be independently controlled by the knob 21 on the amplifier25 its eifect on the reproduced picture may be controlled and thecharacter of the background may be adjusted as desired from very brightto almost black if the function of the cell is cut down low enough.

This effect may also be varied by the distance the screen 2| ispositioned from the object being televised. If it is close to theobject, the cells [6 will receive background light by reflectionsimilarly to the manner in which they have functioned heretofore, whileif it is placed far enough away the reflected light to the cells l6 maybe practically eliminated. But the projected light of the flying spotwill always be strong enough on the ground glass to afiect the operationof the cells22.

The invention provides a very flexible control system which permitschanging the character of the background while the picture is beingtransmitted. If the received image of a face, for instance, tends toblend with ashadowy background, 55

the background may be brightened and the face brought out in contrast byincreasing the output signal from the amplifier 25, and in case thecharacter of the scene changes as where the person moves out of thepicture or several persons suddenly move back into it the background maybe immediately adjusted to meet the requirements without disturbing thephysical set up.

In Fig. 2 is shown a means whereby the effect of the light cell may becontrolled mechanically instead of electrically. Here a glass plate 29is shown positioned in front of the cell 22. This glass is completelytransparent at its upper end-30 but is darkened towards its lower end 3|where it is completely blackened. By moving the glass plate up and downin front of the cell it is possible to prevent any of the light fromentering the cell or to permit as much light to affect it as desired.

While one light cell has been shown behind the background screen 2| itwill be evident that any number of cells may be used for this purposeand that the cells may be positioned in any desired manner, it beingdesirable, however, that they be influenced by all of the light strikingthe screen 2| and for this reason the screen 2| should be made of ahighly diifracting material. Ground glass having a fine uniform surfaceis suitable for this purpose. It is also understood that any number oflight-sensitive cells may be used in front of the object, and that thesecells may be connected in any desirable way, and that any type ofscanning apparatus be used for projecting the swiftly moving spot oflight upon the object to be televised. A translucent screen with cellsbehind it may be preferred but a white diffusing screen may be used withthe cells facing the front of it.

The invention has thus far been described in connection with a flyingspot system of transmission but is applicable also to one in which theobject is illuminated'and the light-sensitive cell is positioned wherethe are light is shown in Fig. 1. The light-sensitive cells l6 and 22would then be replaced by lights which would illuminate the object andtranslucent background screen respectively. In this case also theadjustment of the light upon the screen will control the illumination ofthe background.

With the arrangement just referred to the background screen may also bea white diffusing screen independently illuminated by lights in front ofit.

In view of these and other changes which may be made I do not desire tolimit myself to the specific construction shown and described except assuch limitations occur in the appended claims.

What I claim is:

l. A television transmitting system comprising a light source, means todirect the light from said source in a series of moving spots of lightacross the object to be televised, a light-sensitive cell positioned soas to receive light reflected from said object, means to amplify theimpulses received by said cell, and means behind said object tointercept the light from said light directing means except thatintercepted by the object and to translate said light into electricalimpulses.

2. A television transmitting system comprising means for creating aflying spot of light across an object field, a light-sensitive cellpositioned so as to receive light from said spot reflected from anobject to be televised, and a light-sensitive cell behind said object tobe televised and positioned in such a manner as to receive all lightWithin the object field of said flying spot which is not intercepted bysaid object.

3. A television transmitting system comprising means to create a flyingspot of light across an object field of predetermined area, alight-sensitive cell so positioned that it will receive light from saidflying spot reflected from an object placed within the area of saidobject field, means to amplify the impulses set up by said cell, alightsensitive cell positioned behind said object, means to direct intosaid cell all of the light traversing said object field except thatintercepted by said object, and means to amplify the impulses set up bysaid last mentioned cell.

4. A televisiontransmitting system comprising means to create a flyingspot of light across an object field of predetermined area, alight-sensitive cell so positioned that it will receive light from saidflying spot reflected from an object placed within the area of saidobject field, means to amplify the impulses set up by said cell, alightsensitive cell positioned behind said object, means to direct intosaid cell all of the light traversing said object field except thatintercepted by said object, means to amplify the impulses set up by saidlast mentioned cell, and means to alter the effect of said lastmentioned cell.

5. A television transmitting system comprising means to create a flyingspot of light across a predetermined object field, means to translatevariations of light and shade reflected from an object placed in saidobject field into electrical impulses, means to amplify said impulses,means within said object field to translate the direct light of saidflying spot into electrical impulses, means to amplify said impulses,and means to direct all of the light within said object field exceptthat intercepted by said object into said last mentioned translatingmeans.

6. A television transmitting system comprising means to create a flyingspot of light across a predetermined object field, means to translatevariations of light and shade reflected from an object placed in saidobject field into electrical impulses, means to amplify said impulses,means within said object field to translate the direct light of saidflying spot into electrical impulses, means to amplify said impulses,means to direct all of the light within said object field except thatintercepted by said object into said last mentioned translating means,and means to adjust the output of said last mentioned translating means.

'7. A television transmitting system comprising a translucent screen,means to create a flying spot of light across said translucent screen,means to translate variations of light and shade reflected from anobject placed between said screen and said means into electricalimpulses, and a lightsensitive cell positioned behind said screen insuch a way as to respond to light falling on any portion of said screen.

8. A television transmitting system comprising a translucent screen,means to create a flying spot of light across said translucent screen,means to translate variations of light and shade reflected from anobject placed between said screen and said means into electricalimpulses, a light-sensitive cell positioned behind said screen in such away as to respond to light falling on any portion of said screen, andmeans to control the output of said last mentioned cell.

9. A television transmitting system comprising means to translate thelight and shade values of an object field successively in a series ofscanned lines into electric impulses, means to control the strength ofthe impulses received from an object placed within said object field,and means to independently control the impulses produced from thebackground of the object field.

10. A television transmitting system comprising means for creatingaflying spot of light across an object field, a light-sensitive cellpositioned so as to receive light from said spot refiected from anobject to be televised, a second light-sensitive cell behind said objectto be televised and positioned in such a manner as to receive all lightwithin the object field of said flying spot which is not intercepted bysaid object, and means to combine the impulses of said cells to form onetelevision signal.

11. A television transmitting system comprising means for creating aflying spot of light across an object field, a light-sensitive cellpositioned so as to receive light from said spot reflected from anobject to be televised, a second light-sensitive cell behind said objectto be televised and positioned in such a manner as to receive all lightwithin the object field of said flying spot which is not intercepted bysaid object, means to combine the impulses of said cells to form onetelevision signal, and means to adjust the ratio of the output of saidcells.

12. A television transmitting system comprising means to create a flyingspot of light across a predetermined object field, means to translatevariations of light and shade reflected from an object placed in saidobject field into electrical impulses, means to amplify said impulses,means within said object field to translate the direct light of saidflying spot into electrical impulses, means to amplify said impulses,means to direct all of the light within said object field except thatintercepted by said object into said last mentioned translating means,and means to combine both of said impulses into a single televisionsignal.

13. A television transmitting system comprising, in combination, atranslucent screen in front of which the object to be televised may bepositioned, means to translate the light values of said screen andobject successively in a series of scanned lines into electricalimpulses, means to control the strength of the impulses received fromsaid object, and means to independently control the impulses producedfrom that part of said screen which forms the background for saidobject.

14. A television transmitting system comprising, in combination, a,screen in front of which the object to be televised may be positioned,means to translate the light values of said screen and objectsuccessively in a series of scanned 25 ROBERT HARDING, J R.

